Senna undulata

  • Title

    Senna undulata

  • Author(s)

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna undulata (Benth.) H.S.Irwin & Barneby

  • Description

    27.  Senna undulata (Bentham) Irwin & Barneby, comb. nov. Cassia undulata Bentham, J. Bot. (Hooker) 2: 76. 1840.—"Woods skirting the savannahs. British Guiana. Schomburgk, n. 86.—Trinidad, Lockhart."— Lectoholotypus (Britton & Rose, 1930, p. 238, by implication): Schomburgk 86, collected in 1836, K (hb. Benth.)! = IPA Neg. 86 = NY Neg. 1442; isotypi, †B = F Neg. 1761, F, and locality ‘Essequibo,’ K, US! paratypus, Lockhart s.n., K (hb. Benth.)!—Chamaefistula undulata (Bentham) Pittier, Trab. Mus. Com. Venez. 3: 121. 1928.

    Cassia bimarginata Grisebach, Bonplandia 6: 5. 1858.—Panama, Duchassaing.—No typus found at GOETT, possibly lost at †B, but the description detailed and concordant with S. undulata; overlooked by Bentham, 1871.

    Cassia undulata sensu Bentham, 1871, p. 523; Schery, 1951, p. 77; Croat, Fl. Barro Colorado I. fig. 276. 1978.

    Chamaefistula undulata sensu Britton & Rose, 1930, l.c.

    Awkwardly diffuse or ascending, weakly woody shrubs 1-3 m with more or less plagiotropic branches but in hedges, in forest-savanna ecotone and low forest becoming sarmentose-arborescent or vinelike up to 6 m, the flowering branches then often pendulous from the canopy, the annotinous and older branches subterete striate but the young flowering branchlets strongly angulate-ribbed, highly variable in density and orientation of vesture, the branchlets, lf-stalks, lower face of lfts and inflorescence either strigulose or pilosulous with truly appressed, incumbent or erect hairs up to 0.1-0.5 mm, the foliage strongly bicolored, the thinly chartaceous, relatively small lfts above dark (when dry often brownish-) green and most commonly lustrous and glabrous or almost so, beneath pale dull finely appressed-puberulent (rarely glabrous or pilosulous throughout), the inflorescence variable in form and complexity, either thyrsiform-leafy throughout or at length (especially from canopy) amply thyrsiform-paniculate and at least distally leafless.

    Stipules erect amplexicaul, falcately oblanceolate, linear-oblanceolate or -elliptic, sharply acute or acuminate (5-)6-13(-15) x (1-) 1.5-3.5(-4) mm, prominently 1-3-nerved from base, the principal nerves again branched, the blades thinly herbaceous green or yellowish, normally deciduous before the lf.

    Lvs (below inflorescence) 7-16(-17.5) cm; petiole including livid wrinkled, often twisted pulvinule 15-37 mm, at middle 0.7-1.2(-1.4) mm diam, not or scarcely widened toward the pulvinules, bluntly carinate dorsally, openly shallow-sulcate ventrally; rachis 9-27(-30) mm, almost always shorter than petiole; glands between each pair of pulvinules erect sessile or commonly shortly stipitate, including glabrous or rarely puberulent stipe 1-3.7(-4.5) mm, the always glabrous body ovoid, lance-ovoid, ellipsoid or narrowly fusiform, obtuse or acute; pulvinules 2-4 mm, wrinkled, often livid; distal pair of lfts obliquely lance-, elliptic- or ovate-acuminate, the acumen usually obtuse mucronulate, the blade 5-10.5 x 1.7-4 cm, ±2-3.3 times as long as wide, at strongly asymmetric base varying with increasing amplitude from cuneate to shallowly cordate, the margin strongly revolute and commonly also undulate, the forwardly incurved midrib shallowly depressed-sulcate above, cariniform beneath, the ±8-12(-15) pairs of major camptodrome secondary veins finely prominulous on both faces, the tertiary and (rarely, in Venezuela) delicate reticular venulation also prominulous at least beneath; proximal pair of lfts similar but only 1/2-1/3 as long, sometimes proportionately wider.

    Racemes axillary to living but upward to progressively reduced or ultimately rudimentary lvs, solitary or rarely paired, ascending toward the meridian and consequently appearing divaricate from plagiotropic and reflexed from pendulous branchlets, densely or rather loosely (3-)4-20(-22)-fld, the fls either subcorymbose or becoming racemose, the axis including short peduncle 1.5-7(-11) cm; bracts submembranous yellow or greenish-yellow, rhombic-ovate to lance-elliptic acute or attenuate (6-)7-15 x (2-)2.5-7 mm, puberulent dorsally, delicately venulous in age, persisting at least into full anthesis, often thereafter but seldom into fruit; pedicels 1.5-3 cm; young fl-buds subglobose, finely and usually densely silky-puberulent (-pilosulous), the sepals expanding long before maturity of fl; sepals little graduated, obovate-suborbicular or oblong-obovate, the outermost cucullate, the largest inner ones becoming (5.5-)6-8.5 mm, these (or all) rather prominently 5-7-nerved from base; petals yellow ("orange"), puberulent dorsally at least along veins and sometimes also ventrally, subhomomorphic except the adaxial one a little broader and the 2 abaxial a trifle longer and narrower, in outline oblong- or elliptic-obovate beyond the short claw, the longest of fully expanded fls 12-17(-20) mm, but those of many apparently perfect fls not fully developing and only 9-12 mm; androecium functionally 7-merous, the filaments thinly puberulent (hispidulous), those of 4 median stamens 1-2 mm, of 3 abaxial ones 2.5-4 mm, the anthers glabrous or minutely puberulent in the grooves, those of 4 median stamens 5-8 mm truncate, shallowly incurved, the divaricate 2-porose beak ±0.5 mm, those of 3 abaxial ones 2.8-4.5(-5) mm, the beak as in the median ones or a trifle longer and more porrect; ovary densely whitish-strigulose or -pilosulous, the incurved style moderately dilated and 0.6-1.2 mm diam just below the stigma, the ciliolate orifice 0.4-0.8 mm diam; ovules (96-) 108-164.

    Pod pendulous, the stout stipe 2-4 mm, the straight or slightly incurved body subcylindric 8-20(-26) x 0.9-1.2 cm, the sutures 1.5-2 mm wide, without obvious thickened border, the valves firm, green turning brown, stramineous or ultimately blackish, the dehiscence tardy, follicular; seeds biseriate, turned broadside to the pulpy septa, compressed-ovoid-oblong 4.8-5.2 mm, the testa dark brown moderately lustrous, exareolate.—Collections: 178.

    Savanna thickets, forest-margins, secondary brush woodlands and hedges, in its Caribbean range entering pine-savanna, semideciduous woodland and beach- coppice, mostly in light sandy or porous calcareous soils below 500 m but ascending on Guayana Highland to 1200 and in n.-w. Venezuela to 1450 m, interruptedly widespread over parts of North and Central America, from n.-e. Brazil (Amazon valley in Para and sources of Rio Branco in Terr, do Roraima) and adjoining Guyana through the Orinoco delta to Trinidad and Windward Is. (St. Vincent; not known from Tobago); submontane in n.-w. Venezuela and adjacent Colombia (Cordilleras Oriental and Costanera from Norte de Santander to Ya- racuy); Magdalena valley in n. Colombia (Tolima n.-ward); centr. Panama (Veragua and Canal Zone); n.-w. Costa Rica (Guanacaste and Alajuela); Mosquito Coast of e. Honduras (Gracias a Dios) and Nicaragua (Comarca del Cabo; Zelaya) and Costa Rica (Limon); not recorded from El Salvador; reappearing abundantly in Belize and more sparingly in adjoining Guatemala (Peten; Alta Verapaz); Yucatan Peninsula (e. Tabasco to Yucatan and Quintana Roo) and Chiapas in Mexico.—Fl. intermittently through the year.—Cigarronero; botonero (Venezuela).

    Senna undulata is the only member of ser. Bacillares in which two petiolar glands coincide with enlarged sepaloid floral bracts. Except for these colored bracts and a usually less dilated style the species closely resembles at all points small-leaved states of S. quinquangulata, of which it could perhaps as well be styled a geographic variety. Ease of recognition in practice and a vicariant dispersal under seasonally drier climatic conditions are the feeble justifications for maintaining S. undulata in its traditional specific status.